Gives all catapults a SelectionGroupName, gives all bolt shooters a SelectionGroupName, and gives all siege towers a SelectionGroupName. This means that if you have catapults from different civs because you captured an enemy catapult, double clicking on a catapult will select all of them regardless of civ and also regardless of packed/unpacked status. (If you wish to select only the packed catapults from a specific civ or only the unpacked catapults from a specific civ, you can triple click.)
Note: This patch previously was about how ptol catapults unpacked into mace catapults. Because discussion on D1473 has become controversial regarding SelectionGroupNames, the fix for the ptol/mace catapult issue has been removed from D1473 and split off into D1474.